Western allies on Wednesday promised to make Russia pay for its invasion of Ukraine, as governments and private investors met to fund the country's reconstruction from the ravages of war.

The World Bank has put an estimate of $14 billion on Ukraine's immediate needs for repairing the damage caused by the bitter fighting.

But a recent study by the World Bank, the UN, the European Union and the Ukrainian government said the wider recovery of the economy would cost $441 billion.

"Let's be clear: Russia is causing Ukraine's destruction," US Secretary of State Antony Blinken told delegates at the London conference.

"And Russia will eventually bear the cost of Ukraine's reconstruction," he added.

UK Prime Minister Rishi Sunak voiced a similar message, promising to keep tough sanctions in place "until Russia pays up", and use seized assets to get Ukraine back on its feet.

In the conflict overnight, Russia said it had downed three Ukrainian drones in the Moscow region, while Ukraine said its air defence systems had shot down six Iranian-designed attack drones in the west.

The conference comes as President Volodymyr Zelensky oversees a military fight-back by his troops using Western-supplied heavy weaponry to regain territory lost to Russian forces since last year.

"Every day of Russian aggression brings new ruins, thousands and thousands of destroyed houses, devastated industries, burnt lives," Zelensky told the London delegates by videolink.

But he set out his stall for future investment in Ukraine, saying that despite the devastation, the country was ripe for development in sectors from technology and green agriculture to clean energy.

International help for Ukraine would send a strong message to the world for generations to come, he said.

"Also, the world is watching to see if we will restore normal life in such a way that our transformation will land an ideological defeat on the aggressor.

"We protect Ukraine, and thus we protect freedom. And when we build Ukraine, we'll build freedom."

- Seized assets -

Leaders and representatives from more than 60 countries are attending the International Ukraine Recovery Conference 2023 -- the second to be held since the Russian invasion in February last year.

The first, in Lugano, Switzerland, in July last year saw Kyiv's allies commit to supporting Ukraine through what is expected to be an eye-wateringly expensive and decades-long recovery.

African countries, though, have voiced concern that by pumping aid to Ukraine, the West is backing off from its pledges to help the continent with development and fight climate change.

Sunak told delegates that Kyiv's allies would support Ukraine "on the battlefield and beyond" for as long as it takes.

He has announced UK backing for Ukraine to the tune of $3 billion so it can unlock vital World Bank loans to help bolster its public services, including schools and hospitals.

The guarantee will run over the next three years, he said. He also announced an extra £240 million ($306 million) in development aid funding for humanitarian projects.

European Commission president Ursula von der Leyen recapped the EU executive's support package for Ukraine of 50 billion euros ($55 billion) over the next four years. 

The European Union would soon outline how it intends to use proceeds from seized Russian assets, she added, "because the perpetrator has to be held accountable". 

Germany will provide 381 million euros in humanitarian assistance this year, Foreign Minister Annalena Baerbock said.

Blinken announced more than $1.3 billion in additional US aid. 

"As Russia continues to destroy, we are here to help Ukraine rebuild -- rebuild lives, rebuild its country, rebuild its future," he said.

- Private sector -

As well as government support from around the world, it is hoped more private-sector firms will help in the reconstruction effort.

Delegates include captains of industry from major multinationals and corporations, many of whom have signed up to a new Ukraine Business Compact.

It encourages trade, investment and expertise-sharing to Ukraine on the back of promises from Zelensky to tackle corruption, improve financial and legal transparency, as well as market liberalisation and competition.

Sunak said more than 400 companies from 38 countries, with a combined market capitalisation of $4.9 trillion, have already promised to back Ukraine's recovery and reconstruction.

A new London-based insurance scheme would help to underwrite risky investments in Ukraine, he said, "removing one of the biggest barriers and giving investors the confidence they need to act".

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